Naphthyridine derivatives, their preparation and their use as phosphodiesterase isoenzyme 4 (pde4) inhibitors

ABSTRACT

The invention relates to compounds of formula I  
                 
 
     in free or salt form, where R 1  is a monovalent aromatic group having up to 10 carbon atoms, and R 2  is a cycloaliphatic group having up to 8 ring carbon atoms. Compositions containing them, methods for their preparation and their use as pharmaceuticals are also described.

[0001] This invention relates to organic compounds, their preparationand their use as pharmaceuticals.

[0002] In one aspect, the present invention provides compounds offormula I

[0003] in free or salt form, where

[0004] R¹ is a monovalent aromatic group having up to 10 carbon atoms,and

[0005] R² is a cycloaliphatic group having up to 8 ring carbon atoms.

[0006] “C₁-C₈-alkyl” as used herein denotes straight chain or branchedC₁-C₈-alkyl, which may be, for example, methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, straight orbranched pentyl, straight or branched hexyl, straight or branchedheptyl, or straight or branched octyl. Preferably, C₁-C₈-alkyl isC₁-C₄-alkyl.

[0007] “C₁-C₈-alkoxy” as used herein denotes straight chain or branchedC₁-C₈-alkoxy which may be, for example, methoxy, ethoxy, n-propoxy,isopropoxy, n-butoxy, isobutoxy, sec-butoxy, tert-butoxy, straight orbranched pentoxy, straight or branched hexyloxy, straight or branchedheptyloxy, or straight or branched octyloxy. Preferably, C₁-C₈-alkoxy isC₁-C₄-alkoxy.

[0008] “C₁-C₈-alkylthio” as used herein denotes straight chain orbranched C₁-C₈-alkylthio, which may be, for example, methylthio,ethylthio, n-propylthio, isopropylthio, n-butylthio, isobutylthio,sec-butylthio, tert-butylthio, straight or branched pentylthio, straightor branched hexyltliio, straight or branched heptylthio, or straight orbranched octylthio. Preferably, C₁-C₈-alkylthio is C₁-C₄-alkylthio.

[0009] “C₁-C₈-haloalkyl” as used herein denotes C₁-C₈-alkyl ashereinbefore defined substituted by one or more halogen atoms,preferably one, two or three halogen atoms.

[0010] “C₁-C₈-haloalkoxy” as used herein denotes C₁-C₈-alkoxy ashereinbefore defined substituted by one or more halogen atoms,preferably one, two or three halogen atoms.

[0011] “C₃-C₈-cycloalkyl” as used herein denotes cycloalkyl having 3 to8 ring carbon atoms, for example a monocyclic group such as acyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl orcyclooctyl, any of which can be substituted by one or more, usually oneor two, C₁-C₄-alkyl groups, or a bicyclic group such as bicycloheptyl orbicyclooctyl. Preferably “C₃-C₈-cycloalkyl” is cyclopropyl, cyclobutyl,cyclopentyl, cyclohexyl, cycloheptyl or cyclooctyl.

[0012] “Acyl” as used herein denotes alkylcarbonyl, for exampleC₁-C₈-alkylcarbonyl where C₁-C₈-alkyl may be one of the C₁-C₈-alkylgroups hereinbefore mentioned, optionally substituted by one or morehalogen atoms; cycloalkylcarbonyl, for example C₃-C₈-cycloalkylcarbonylwhere C₃-C₈-cycloalkyl may be, for example, cyclopropyl, cyclobutyl,cyclopentyl, cyclohexyl, cycloheptyl or cyclooctyl; 5- or 6-memberedheterocyclylcarbonyl having one or two hetero atoms selected fromnitrogen, oxygen and sulfur in the ring, such as furylcarbonyl,tetrahydrofurylcarbonyl, pyrrolidinylcarbonyl, piperidinylcarbonyl orpyridylcarbonyl; arylcarbonyl, for example C₆-C₁₀-arylcarbonyl such asbenzoyl; or aralkylcarbonyl, for example C₆ toC₁₀-aryl-C₁-C₄-alkylcarbonyl such as benzylcarbonyl orphenylethylcarbonyl.

[0013] “C₁-C₈-alkoxycarbonyl” as used herein denotes C₁-C₈-alkoxy ashereinbefore defined linked through an oxygen atom thereof to a carbonylgroup.

[0014] “C₁-C₈-haloalkoxycarbonyl” as used herein denotesC₁-C₈-haloalkoxy as hereinbefore defined linked through an oxygen atomthereof to a carbonyl group.

[0015] “C₁-C₈-hydroxyalkoxycarbonyl” and“C₁-C₈-alkoxy-C₁-C₈-alkoxycarbonyl” as used herein denoteC₁-C₈-alkoxycarbonyl as hereinbefore defined in which the C₁-C₈-alkoxygroup is substituted by hydroxy or a further C₁-C₈-alkoxy grouprespectively.

[0016] “Carboxy-C₁-C₈-alkoxy” as used herein denotes C₁-C₈-alkoxy ashereinbefore defined substituted by carboxy.

[0017] “Halogen” or “halo” as used herein may be fluorine, chlorine,bromine or iodine; preferably it is fluorine, chlorine or bromine.

[0018] R¹ may be, for example, phenyl optionally substituted by one ormore electron-withdrawing substituents, preferably selected from cyano,halogen, carboxy, aminocarbonyl, C₁-C₈-haloalkyl or C₁-C₈-haloalkoxy,preferably one or two such substituents, and/or optionally substitutedby C₁-C₈-alkyl, hydroxy, C₁-C₈-alkoxy or C₁-C₈-alkylthio, or R¹ may be aheterocyclic aromatic group having up to 10 ring atoms and 1 to 4 ringhetero atoms, preferably selected from nitrogen, oxygen and sulfur, forexample a heterocyclyl group such as furyl, thienyl, pyrrolyl,imidazolyl, pyrazolyl, furazanyl, triazolyl, tetrazolyl, oxazolyl,isoxazolyl, thiazolyl, pyridyl, pyrimidyl, pyridazinyl, triazinyl,indolyl, isoindolyl or benzimidazolyl, which heterocyclyl group may beunsubstituted or substituted e.g. by at least one C₁-C₈-alkyl, halogenor C₁-C₈-alkoxy. Preferred groups R¹ include (a) phenyl substituted bycyano, halogen (particularly fluorine or chlorine), carboxy orC₁-C₄-haloalkoxy, and optionally by C₁-C₄-alkyl or C₁-C₄-alkoxy, (b)phenyl substituted by C₁-C₄-alkoxy and (c) an aromatic heterocyclicgroup having 5 or 6 ring atoms and one or two ring hetero atoms.

[0019] R² may be, for example, a C₃-C₈-cycloalkyl group such ascyclopropyl, methylcyclopropyl, cyclobutyl, cyclopentyl,methylcyclopentyl, cyclohexyl, methylcyclohexyl, dimethylcyclohexyl,cycloheptyl, bicycloheptyl or cyclooctyl, optionally substituted by atleast one substituent selected from C₁-C₈-alkyl, C₁-C₈-alkoxy, carboxy,C₁-C₈-alkoxycarbonyl, C₁-C₈-haloalkoxycarbonyl,C₁-C₈-hydroxyalkoxycarbonyl, C₁-C₈-alkoxy-C₁-C₈-alkoxycarbonyl,aminocarbonyl, C₁-C₈-alkylarminocarbonyl, di(C₁-C₈-alkyl)aminocarbonyl,hydroxy, acyl or C₁-C₈-alkyl optionally substituted by hydroxy, cyano,carboxy or C₁-C₈-alkoxycarbonyl. Preferably, R² is C₅-C₇-cycloalkylsubstituted by C₁-C₄-alkyl, carboxy, C₁-C₈-alkoxy-carbonyl oraminocarbonyl.

[0020] Preferred compounds of formula I in free or salt form includethose where

[0021] R¹ is phenyl substituted by one or two substituents selected fromcyano, halogen, carboxy or aminocarbonyl, and optionally byC₁-C₈-alkoxy, or R¹ is phenyl substituted by C₁-C₄-alkoxy, hydroxy orC₁-C₄-alkylthio, and

[0022] R² is C₃-C₈-cycloalkyl optionally substituted by at least onesubstituent selected from C₁-C₄-alkyl, carboxy, C₁-C₈-alkoxycarbonyl oraminocarbonyl.

[0023] Further preferred compounds of formula I in free or salt forminclude those where

[0024] R¹ is phenyl substituted by one of two substituents selected fromcyano, halogen, carboxy or aminocarbonyl meta to the indicatednaphthyridine ring and optionally by C₁-C₄-alkoxy ortho to the indicatednaphthyridine ring, or R¹ is phenyl substituted by C₁-C₄-alkoxy meta tothe indicated naphthyridine ring, and

[0025] R² is C₅-C₇-cycloalkyl optionally substituted by at least onesubstituent selected from carboxy and C₁-C₄-alkoxycarbonyl.

[0026] Other preferred compounds of formula I in free or salt forminclude those where

[0027] R¹ is phenyl optionally substituted by one, two or threesubstituents selected from the group consisting of halo, cyano,C₁-C₈-alkyl, C₁-C₈-alkylthio, —SO—C₁-C₈-alkyl, C₁-C₈-alkoxy andC₁-C₈-haloalkoxy, or phenyl fused with a heterocyclic ring having 3 to 8ring atoms of which up to 4 can be carbon atoms and up to 4 can behetero atoms; and

[0028] R² is C₃-C₈-cycloalkyl optionally substituted by at least onesubstituent selected from the group consisting of carboxy andcarboxy-C₁-C₈-alkoxy,

[0029] Further preferred compounds of formula I in free or salt forminclude those where

[0030] R¹ is phenyl optionally substituted by one, two or threesubstituents selected from the group consisting of halo, cyano,C₁-C₄-alkyl, C₁-C₄-alkylthio, —SO—C₁-C₄-alkyl, C₁-C₄-alkoxy andC₁-C₄-haloalkoxy, or phenyl fused with a heterocyclic ring having 5 or 6ring atoms of which up to 4 can be carbon atoms and up to 2 can behetero atoms; and

[0031] R² is C₅-C₇ cycloalkyl optionally substituted by at least onesubstituent selected from the group consisting of carboxy andcarboxy-C₁-C₄-alkoxy.

[0032] The compounds represented by formula I are capable of formingacid addition salts, particularly pharmaceutically acceptable acidaddition salts. Pharmaceutically acceptable acid addition salts of thecompounds of formula I include those of inorganic acids, for example,hydrohalic acids such as hydrofluoric acid, hydrochloric acid,hydrobromic acid or hydroiodic acid, nitric acid, sulfuric acid,phosphoric acid; and organic acids, for example aliphatic monocarboxylicacids such as formic acid, acetic acid, trifluoroacetic acid, propionicacid and butyric acid, aliphatic hydroxy acids such as lactic acid,citric acid, tartaric acid or malic acid, dicarboxylic acids such asmaleic acid or succinic acid, aromatic carboxylic acids such as benzoicacid, p-chlorobenzoic acid, diphenylacetic acid or triphenylacetic acid,aromatic hydroxy acids such as o-hydroxybenzoic acid, p-hydroxybenzoicacid, 1-hydroxynaphthalene-2-carboxylic acid or3-hydroxynaphthalene-2-carboxylic acid, and sulfonic acids such asmethanesulfonic acid or benzenesulfonic acid.

[0033] These salts may be prepared from compounds of formula I by knownsalt-forming procedures.

[0034] Compounds of formula I which contain acidic, e.g. carboxyl,groups, are also capable of forming salts with bases, in particularpharmaceutically acceptable bases such as those well known in the art;suitable such salts include metal salts, particularly alkali metal oralkaline earth metal salts such as sodium, potassium, magnesium orcalcium salts, or salts with ammonia or pharmaceutically acceptableorganic amines or heterocyclic bases such as ethanolamines, benzylaminesor pyridine. These salts may be prepared from compounds of formula I byknown salt-forming procedures.

[0035] The compounds of formula I in free or salt form may exist instereoisomeric forms according to the orientation of moieties attachedto the cycloaliphatic ring. The invention embraces both individual suchstereoisomers, i.e. cis and trans isomers, as well as mixtures thereof.Where R¹ or R² contain an asymmetric carbon atom, the compounds offormula I in free or salt form exist in individual optically activeisomeric forms or as mixtures thereof, e.g. as racemic or diastereomericmixtures. The invention embraces both individual optically active R andS isomers as well as mixtures, e.g. racemic or diastereomeric mixtures,thereof.

[0036] Specific especially preferred compounds of formula I are thosedescribed hereinafter in the Examples.

[0037] The present invention also provides a process for the preparationof compounds of formula I in free or salt form which comprises

[0038] (i) (A) reacting a compound of formula II

[0039] optionally in protected form, where R¹ is as hereinbefore definedand L is a leaving atom or group, for example halogen or an aliphatic oraromatic sulfonyloxy group such as trifluoromethylsulfonyloxy, with acompound of formula III

X—R²  III

[0040] optionally in protected form, where R² is as hereinbefore definedand X is a leaving atom or group which is reactive with L in formula IIto form a direct bond between R² and the indicated naphthyridine ring,followed by deprotection if required;

[0041] (B) reacting a compound of formula I, where R² is cycloalkylsubstituted by a C₁-C₈-alkoxycarbonyl group, to convert thealkoxycarbonyl group into a carboxy group;

[0042] (C) for the preparation of compounds of formula I where R² is acycloaliphatic group substituted by carboxy-C₁-C₈-alkoxy, hydrolysing acompound of formula I where R² is a cycloaliphatic group substituted byC₁-C₈-alkoxycarbonyl-C₁-C₈-alkoxy; or

[0043] (D) for the preparation of compounds of formula I when R¹ isphenyl substituted by —SO—C₁-C₈-alkyl, oxidising a compound of formula Iwhere R¹ is phenyl substituted by C₁-C₈-alkylthio; and

[0044] (ii) recovering the product in free or salt form.

[0045] Where L in formula II is an aromatic sulfonyloxy group, X may be,for example, a group YM- where Y is halogen such as iodine and M is ametal such as zinc or magnesium.

[0046] Process variant (A) may be effected using known procedures forreaction of leaving atoms or groups or analogously, for example ashereinafter described in the Examples. Where X in formula III is YM-,the compound YMR² may be formed in situ by reaction of the metal M andthe halide YR²; where M is zinc, this in situ reaction is convenientlyeffected in the presence of dibromoethane and a trialkylsilyl halide,preferably in a solvent, e.g. an ether such as tetrahydrofuran (THF),convenient reaction temperatures being from 25 to 50° C. Reaction of thecompound of formula II with YMR² may be effected in the presence of atransition metal catalyst, particularly a palladium-ketone complexcatalyst, 1,1′-bis(diphenyl-phosphino)ferrocene and a quaternaryammonium halide such as tetrabutylammonium iodide, conveniently in asolvent, e.g. a mixture of an ether such as THF andN-methyl-pyrrolidone(NMP), convenient reaction temperatures being from25 to 50° C. Where it is desired to minimise the possibility of reactionof functional groups other than those participating in the desiredreaction, such functional groups may be protected by conventionalprotecting groups.

[0047] Process variant (B) may be effected using known procedures forconversion of alkoxycarbonyl groups to carboxy groups, e.g. hydrolysiswith an aqueous alkali metal hydroxide, or analogously such ashereinafter described in the Examples.

[0048] Process variant (C) may be effected using art known proceduresfor the hydrolysis of esters to carboxylic acids, e.g. usingtrifluoroacetic acid, or analogously such as hereinafter described inthe Examples.

[0049] Process variant (D) may be effected using art known proceduresfor the oxidation of sulfanyl groups to sulfinyl groups, e.g. usingozone or hydrogen peroxide, or analogously such as hereinafter describedin the Examples.

[0050] Compounds of formula II may be prepared as described inWO98/18796 or analogously, for example as hereinafter described in theExamples. Compounds of formula III may be prepared by known procedures,for example in situ as described hereinbefore and (in the Examples)hereinafter.

[0051] Where reference is made herein to protected functional groups orto protecting groups, the protecting groups may be chosen in accordancewith the nature of the functional group, for example as described inProtective Groups in Organic Synthesis, T. W. Greene and P. G. M. Wuts,John Wiley &c Sons Inc, Second Edition, 1991, which reference alsodescribes procedures suitable for replacement of the protecting groupsby hydrogen.

[0052] Compounds of formula I in free form may be converted into saltform, and vice versa, in a conventional manner. The compounds in free orsalt form can be obtained in the form of hydrates or solvates containinga solvent used for crystallization. Compounds of formula I can berecovered from reaction mixtures and purified in a conventional manner.Isomers, such as enantiomers, may be obtained in a conventional manner,e.g. by fractional crystallization or asymmetric synthesis fromcorrespondingly asymmetrically substituted, e.g. optically active,starting materials.

[0053] Compounds of formula I in free or salt form are useful aspharmaceuticals. Accordingly the invention also provides a compound offormula I in free or salt form for use as a pharmaceutical. Thecompounds of formula I in free or salt form, hereinafter referred toalternatively as “AGENTS OF THE INVENION”, exhibit cyclic nucleotidephosphodiesterase (PDE) isoenzyme inhibiting activity, selective fortype 4 isoenzyme. AGENTS OF THE INVENTION possess anti-inflammatory,anti-airways hyperreactivity and bronchodilator properties. They furtherpossess immunosuppressive and TNFα secretion inhibitory activities. Thepharmacological activities may be demonstrated in test methods, forexample as follows:

[0054] PDE4 Isoenzyme Inhibition Assay

[0055] Cloning: GATEWAY flanked PDE4 cDNA constructs containing thecoding regions of the three isoenzymes, human PDE4A, human PDE4B, andhuman PDE4D are generated by PCR and transposed into the GATEWAY shuttlevector pDONOR-201. In addition a 6-histidine tag is introduced by PCRonto the carboxyl terminal end of each of the constructs to facilitateprotein purification. Following sequence verification, the PDE4constructs are transposed into the GATEWAY expression vector pDEST-8,Positive recombinants are selected and transposed into E. coli strainDH10Bac and bacmid produced transfected into SF21 cells using Bac-To-Bac(Invitrogen Life Technologies). Positive transfections are selected andused to generate high titer viral stocks for use in protein expression.

[0056] PDE4 Expression: Sf21 cells are grown to a density of 2×106cells/ml and infected with human PDE4A, PDE4B or PDE4D3 containingbaculovirus to a multiplicity of infection (m.o.i.) of 1 for 72 hours.The infected cells are harvested by centrifugation at 1,400 g for 4minutes at 4° C. and the cell pellets are frozen at −80° C. Sf21(Spodoptera frugiperda 21) insect cells are routinely maintained atdensities between 3×105 and 3×106 cells/ml in SF00 Serum Free Medium(Invitorgen Life Technologies). Sf21 cells (1×109) are resuspended in100 ml cold (4° C.) Lysis Buffer (50 mM Na₂HPO4, 200 mM NaCl, 10 mMImidazole). Cells are incubated on ice for 30 minutes then centrifugedat 15,000 g for 20 minutes at 4° C.

[0057] PDE4 Purification: The 6 Histidine-tagged PDE4 proteins areisolated from crude cell lysates by a batch-wise Ni-NTA purificationstrategy (QIAGEN). N-NTA resin is first pre-rinsed to remove ethanolpreservative and equilibrated with Lysis Buffer. Cell lysate is added,(10 ml 50% Ni-NTA slurry resin per 50 ml lysate), and gently rotated ona mixer at 4° C. for 1-2 hours. The sample is then centrifuged at 1,000g for 5 minutes at 4° C. using Denley benchtop centrifuge. Thesupernatant is removed and the resin is washed 3 times with 50 ml icecold Wash Buffer (50 mM Na₂HPO4, 300 mM NaCl and 20 mM imidazole)followed by centrifugation at 1,000 g for 5 min at 4° C. The 6His-taggedprotein is eluted from the resin with 3×5 ml ice cold Elution Buffer (50mM NaH₂PO4, 300 mM NaCl, 250 mM imidazole) and collected bycentrifugation at 1,000 g for 5 minutes at 4° C. The supernatants arethen pooled before buffer exchange and concentration using a VivaScience20 ml SK 0.2 μM Concentrator. Samples are aliquoted and stored at −20°C.

[0058] SDS-PAGE Electrophoresis: Purified PDE4 samples are analysed bySDS-PAGE using 8-16% gradient mini-gels (Novex) and samples aredenatured at 100° C. in reducing sample buffer (62 mM Tris-HCl pH 6.8,10% glycerol, 3% SDS, 5%

-mercaptoethanol, 0.02% bromophenol blue) for 3 min prior to loading.Novex SeeBlue pre-stained MW standards are also loaded. Gels are run ata constant 25 mA. Gels are stained with GelCode Colloidal CoomassieG-250 Blue Stain Reagent (Pierce) according to the manufacturer'sprocedure.

[0059] Western Blot Analysis: Samples are analysed on Novex 8-16%gradient gels as described above. The gel is then wet blotted ontoMillipore Immobilon-P PVDF membrane using the tank transfer method with25 mM Tris-HCl pH 8.8, 192 mM Glycine, 15% methanol transfer buffer at80 mA for 16 h. Immunoprobing is carried out in TTBS buffer (20 mMTris-HCl pH 7.6, 0.9% (w/v) NaCl, 0.05% (v/v) Triton X-100, 0.5% (w/v)casein) with an anti-6his monoclonal antibody (QIAGEN) at 1:1000dilution, An anti-mouse IgG alkaline phosphatase conjugate is used asthe secondary antibody (Sigma A9919) at 1:10000 dilution and proteinsvisualised with BCIP/NBT substrate prepared from tablets (Sigma)according to the manufacturers procedure,

[0060] PDE4 Assay: The assay is based on Amersham Pharmacia BiotechScintillation Proximity Assay (SPA) technology. Enzyme is diluted withenzyme dilution buffer (10 mM Tris-HCl, pH7.5 containing 1 mM EDTA) inorder to obtain between 10-30% total substrate hydrolysis during theassay. The enzymatic reaction is started by adding 10 μl diluted enzymeto 80 μl substrate (0.1 μCi [3H]-cAMP, 1 μM cAMP) and 10 μl inhibitorsolution in a 96-well microtiter plate. After 30-60 minutes incubationat room temperature the reaction is stopped by adding 50 μl PDE SPAbeads (20 mg/ml). After 30 minutes the plate is centrifuged (3000 g, 10minutes) and counted (Packard TopCount).

[0061] Inhibitor stock solutions are prepared in 100% dimethylsulphoxide(DMSO) and diluted with DMSO/water to achieve 10 concentrations to coverthe range of 0-100% inhibition. The concentration of DMSO is keptconstant at 1% (v/v) throughout the assay.

[0062] The concentration at which 50% inhibition occurs (IC₅₀) isdetermined from inhibition-concentration curves in a conventionalmanner. Within the PDE4 isoenzyme group, AGENTS OF THE INVENTIONgenerally exhibit selectivity for inhibition of PDE4D isoenzyme relativeto PDE4A, PDE4B and PDE4C. The compounds of Examples 1, 3, 10, 12, 14and 15 have IC₅₀ values of 38, 9, 25, 21, 57 and 9 nM respectively forinhibition of PDE4D in the above assay.

[0063] Having regard to their inhibition of binding of PDE4, AGENTS OFTHE INVENTION are useful in the treatment of conditions mediated byPDE4, particularly inflammatory conditions. Treatment in accordance withthe invention may be symptomatic or prophylactic.

[0064] Accordingly, AGENTS OF THE INVENTION are useful in the treatmentof inflammatory or obstructive airways diseases, resulting, for example,in reduction of tissue damage, bronchial hyperreactivity, remodelling ordisease progression. Inflammatory or obstructive airways diseases towhich the present invention is applicable include asthma of whatevertype or genesis including both intrinsic (non-allergic) asthma andextrinsic (allergic) asthma, mild asthma, moderate asthma, severeasthma, bronchitic asthma, exercise-induced asthma, occupational asthmaand asthma induced following bacterial or viral infection. Treatment ofasthma is also to be understood as embracing treatment of subjects, e.g.of less than 4 or 5 years of age, exhibiting wheezing symptoms anddiagnosed or diagnosable as “wheezy infants”, an established patientcategory of major medical concern and now often identified as incipientor early-phase asthmatics. (For convenience this particular asthmaticcondition is referred to as “wheezy-infant syndrome”.)

[0065] Prophylactic efficacy in the treatment of asthma will beevidenced by reduced frequency or severity of symptomatic attack, e.g.of acute asthmatic or bronchoconstrictor attack, improvement in lungfunction or improved airways hyperreactivity. It may further beevidenced by reduced requirement for other, symptomatic therapy, i.e.therapy for or intended to restrict or abort symptomatic attack when itoccurs, for example anti-inflammatory (e.g. corticosteroid) orbronchodilatory. Prophylactic benefit in asthma may in particular beapparent in subjects prone to “morning dipping”. “Morning dipping” is arecognised asthmatic syndrome, common to a substantial percentage ofasthmatics and characterised by asthma attack, e.g. between the hours ofabout 4 to 6 am, i.e. at a time normally substantially distant form anypreviously administered symptomatic asthma therapy.

[0066] Other inflammatory or obstructive airways diseases and conditionsto which the present invention is applicable include acute lung injury(ALI), adult/acute respiratory distress syndrome (ARDS), chronicobstructive pulmonary, airways or lung disease (COPD, COAD or COLD),including chronic bronchitis or dyspnea associated therewith, emphysema,as well as exacerbation of airways hyperreactivity consequent to otherdrug therapy, in particular other inhaled drug therapy. The invention isalso applicable to the treatment of bronchitis of whatever type orgenesis including, e.g., acute, arachidic, catarrhal, croupus, chronicor phthinoid bronchitis. Further inflammatory or obstructive airwaysdiseases to which the present invention is applicable includepneumoconiosis (an inflammatory, commonly occupational, disease of thelungs, frequently accompanied by airways obstruction, whether chronic oracute, and occasioned by repeated inhalation of dusts) of whatever typeor genesis, including, for example, aluminosis, anthracosis, asbestosis,chalicosis, ptilosis, siderosis, silicosis, tabacosis and byssinosis,

[0067] Having regard to their anti-inflammatory activity, theirinfluence on airways hyperreactivity and their profile in relation toPDE isoenzyme inhibition, in particular as selective type 4 inhibitors,AGENTS OF THE INVENTION are useful for the treatment, in particularprophylactic treatment, of obstructive or inflammatory airways disease.Thus by continued and regular administration over prolonged periods oftime AGENTS OF THE INVENTION are useful in providing advance protectionagainst recurrence of bronchoconstrictor or other symptomatic attackconsequential to obstructive or inflammatory airways disease or for thecontrol, amelioration or reversal of basal status of such disease.

[0068] Having regard to their bronchodilator activity AGENTS OF THEINVENTION are useful as bronchodilators, e.g. for the treatment ofchronic or acute broncho-constriction, e.g. for the symptomatictreatment of obstructive or inflammatory airways disease.

[0069] Having regard to their activity as selective inhibitors of TNF-αrelease, AGENTS OF THE INVENTION are also useful for the down-regulationor inhibition of TNF-α release, e.g. for the treatment of diseases orconditions in which TNF-α release is implicated or plays a mediatingrole, e.g. diseases or conditions having an aetiology involving orcomprising morbid, for example undesirable, excessive or unregulatedTNF-α release, in particular for the treatment of cachexia or endotoxinshock and in treatment of AIDS [cf. Sharief et al, Mediators ofInflammation, 1 323-338 (1992)], the treatment of cachexia associatedwith morbid TNF-α release or TNF-α blood-serum levels of whateverorigin, including cachexia consequential to, e.g. bacterial, viral orparasitic, infection or to deprivation or deterioration of humoral orother organic, e.g. renal function, the treatment of cancerous, malarialand vermal cachexia, cachexia resulting from dysfunction of thepituitary, thyroid or thymus glands as well as uremic cachexia and, inparticular, the treatment of AIDS-related cachexia, i.e. cachexiaconsequential to or associated with to HIV infection.

[0070] The method of the invention is also applicable to the treatmentof septic shock, e.g., shock conditions resulting from bacterialinfection. In this regard it is to be noted that the present inventionprovides a method for the treatment of septic shock as such as well asof conditions consequential to or symptomatic of septic or shock, forexample ARDS.

[0071] The AGENTS OF THE INVENTION are further applicable to thetreatment of disease consequential to HIV infection, e.g. AIDS, e.g. tothe amelioration or control of the advance of such disease.

[0072] Having regard to their profile in relation to inhibition of PDEisoenzymes and/or TNF-α release inhibition, as well as theirimmunosuppressive activity, AGENTS OF THE INVENTION are also useful asimmunosuppressive agents, e.g. for the treatment of autoimmune diseases,in particular for the treatment of autoimmune diseases in whichinflammatory processes are implicated or which have an inflammatorycomponent or aetiology, or as anti-inflammatory agents for the treatmentof inflammatory disease in particular for the treatment of inflammatorydisease in which autoimmune reactions are implicated or which have anautoimmune component or aetiology. Examples of such disease to which thepresent invention is applicable include autoimmune hematologicaldisorders (e.g. hemolytic anaemia, aplastic anaemia, pure red cellanaemia and idiopathic thrombocytopenia), systemic lupus erythematosus,polychondritis, scleroderma, Wegener granulomatosis, dermatomyositis,chronic active hepatitis, myasthenia gravis, Steven-Johnson syndrome,idiopathic sprue, autoimmune inflammatory bowel disease (e.g. ulcerativecolitis and Crohn's disease), endocrine ophthalmopathy, Grave's disease,sarcoidosis, alveolitis, chronic hypersensitivity pneumonitis, multiplesclerosis, primary biliary cirrhosis, juvenile diabetes (diabetesmellitus type I), uveitis (anterior and posterior), keratoconjunctivitissicca and vernal keratoconjunctivitis, interstitial lung fibrosis,psoriatic arthritis and glomerulonephritis (with and without nephroticsyndrome, e.g. including idiopathic nephrotic syndrome or minimal changenephropathy), as well as inflammatory and/or hyperproliferative skindiseases such as psoriasis, atopic dermatitis, pemphigus and, inparticular, contact dermatitis, e.g. allergic contact dermatitis.

[0073] AGENTS OF THE INVENTION are in particular useful for thetreatment of arthritis, and other rheumatic or inflammatory disease,especially for the treatment of rheumatoid arthritis.

[0074] As immunosuppressants AGENTS OF THE INVENTION are further usefulin the prevention of graft rejection, e.g. for the maintenance ofallogenic organ transplants or the like, e.g. in relation to kidney,liver, lung, heart, heart-lung, bowel, bone-marrow, skin, or cornealtransplant.

[0075] Having regard to their profile in relation to inhibition of PDEisoenzymes, in particular their profile as selective type 4 inhibitors,AGENTS OF THE INVENTION are further useful for the treatment of diseaseinvolving tissue calcium depletion, in particular degenerative diseasesof the bone and joint involving calcium depletion, especiallyosteoporosis. In this regard they are further useful for the treatmentof allergic inflammatory diseases such as rhinitis, conjunctivitis,atopic dermatitis, urticaria and gastrointestinal allergies; asvasodilators, e.g. for the treatment of angina, hypertension,ischaemia/reperfusion injury, congestive heart failure and multi-infarctdementia; and for the treatment of other conditions where inhibition ofPDE 4 is indicated, for example, depression, conditions and diseasescharacterised by impaired cognitive function including Alzheimer'sdisease, Parkinson's disease and stroke.

[0076] The AGENTS OF THE INVENTION are also useful as co-therapeuticagents in combination with other drug substances such asanti-inflammatory, bronchodilatory, antihistamine or immunosuppressivedrug substances, particularly in the treatment of inflammatory diseasese.g. obstructive or inflammatory airways diseases, autoimmune diseasesor graft rejection such as those mentioned hereinbefore, for example aspotentiators of therapeutic activity of such drugs or as a means ofreducing required dosaging or potential side effects of such drugs. Anagent of the invention may be mixed with the other drug substance in afixed pharmaceutical composition or it may be administered separately,before, simultaneously with or after the other drug substance. Suchanti-inflammatory drugs include steroids, in particularglucocorticosteroids such as budesonide, beclamethasone, fluticasone,ciclesonide or mometasone, LTB4 antagonists such as those described inU.S. Pat. No. 5,451,700 and LTD4 antagonists such as montelukast andzafirlukast, dopamine receptor agonists such as cabergoline,bromocriptine, ropinirole and4-hydroxy-7-[2-[[2-[[3-(2-phenylethoxy)propyl]-sulfonyl]ethyl]-amino]ethyl]-2(3H)-benzothiazoloneand pharmaceutically acceptable salts thereof (the hydrochloride beingViozan®-AstraZeneca). Such bronchodilatory drugs include anticholinergicor antimuscarinic agents, in particular ipratropium bromide, oxitropiumbromide and tiotropiurm bromide, and beta-2 adrenoceptor agonists suchas salbutamol, terbutaline, salmeterol and, especially, formoterol andpharmaceutically acceptable salts thereof, and compounds (in free orsalt or solvate form) of formula I of PCT International Publication No.WO 00/175114, which document is incorporated herein by reference,preferably compounds of the Examples thereof, especially a compound offormula

[0077] and pharmaceutically acceptable salts thereof. Co-therapeuticantihistamine drug substances include cetirizine hydrochloride,acetaminophen, clemastine fumarate, promethazine, loratidine,desloratidine, diphenhydramine and fexofenadine hydrochloride.Co-therapeutic immunosuppressive drug substances include, e.g.cyclopeptide, cyclopeptolide or macrolide drug substances, for examplesdrugs belonging to the cyclosporin class, e.g. cyclosporins A or G, thedrug substances tacrolimus (also known as FK 506), ascomycin andrapamycin and their various known congeners and derivatives.

[0078] Combinations of AGENTS OF THE INVENTION and steroids, beta-2agonists, or LTD4 antagonists may be used, for example, in the treatmentof COPD or, particularly, asthma. Combinations of AGENTS OF THEINVENTION and anticholinergic or antimuscarinic agents, PDE4 inhibitors,dopamine receptor agonists or LTB4 antagonists may be used, for example,in the treatment of asthma or, particularly, COPD. Combinations ofAGENTS OF THE INVENTION and immunosuppressive drug substances may beused in the treatment of any disease or condition requiringimmunosuppressive treatment as hereinbefore described.

[0079] Other useful co-therapeutic combinations of AGENTS OF THEINVENTION include combinations with PDE3 inhibitors such as thosedisclosed in WO 00/166123, e.g. revizinone, ci-lostamide, amipizone,siguazodan, carbazeran, bemoradan, motapizone and, particularly,milrinone, enoximone and pimopendan, especially for treatment ofconditions characterised by acute or chronic obstruction of vesselsand/or bronchi and/or acute or chronic inflammation, e.g. acuteobstructive bronchitis, bronchial asthma or COPD.

[0080] In accordance with the foregoing, the present invention alsoprovides a method for the treatment of a disease mediated by PDE4 whichcomprises administering to a subject, particularly a human subject, inneed thereof an effective amount a compound of formula I, or apharmaceutically acceptable salt thereof, as hereinbefore described. Inanother aspect, the invention provides a compound of formula I, or apharmaceutically acceptable salt thereof, as hereinbefore described foruse in the preparation of a medicament for the treatment of a diseasemediated by PDE4.

[0081] In accordance with the foregoing, the present invention alsoprovides a method for the treatment of an inflammatory disease,particularly an obstructive or inflammatory airways disease, whichcomprises administering to a subject, particularly a human subject, inneed thereof an effective amount a compound of formula I, or apharmaceutically acceptable salt thereof, as hereinbefore described. Inanother aspect, the invention provides a compound of formula I, or apharmaceutically acceptable salt thereof, as hereinbefore described foruse in the preparation of a medicament for the treatment of aninflammatory disease, particularly an obstructive or inflammatoryairways disease.

[0082] The AGENTS OF THE INVENTION may be administered by anyappropriate route, e.g. orally, for example in the form of a tablet orcapsule; parenterally, for example intravenously; topically to the skin,for example in the treatment of psoriasis; intranasally, for example inthe treatment of rhinitis; or by inhalation, particularly in thetreatment of obstructive or inflammatory airways diseases.

[0083] In a further aspect, the invention also provides a pharmaceuticalcomposition comprising as active ingredient a compound of formula I infree form or in the form of a pharmaceutically acceptable salt thereof,optionally together with a pharmaceutically acceptable diluent orcarrier therefor. Such compositions may be prepared using conventionaldiluents or excipients and techniques known in the galenic art. Thusoral dosage forms may include tablets, capsules and controlled releaseformulations such as encapsulated or matrix dissolution formulations,osmotic system formulations or ion exchange resin formulations.Formulations for topical administration may take the form of creams,ointments, gels or transdermal delivery systems, e.g. patches.Compositions for inhalation may comprise aerosol or other atomizableformulations or dry powder formulations.

[0084] When the composition comprises an aerosol formulation, itpreferably contains, for example, a hydro-fluoro-alkane (HFA) propellantsuch as HFA134a or HFA227 or a mixture of these, and may contain one ormore co-solvents known in the art such as ethanol (up to 20% by weight),and/or one or more surfactants such as oleic acid or sorbitan trioleate,and/or one or more bulking agents such as lactose.

[0085] When the composition comprises a dry powder formulation, itpreferably contains, for example, a compound of formula I having aparticle diameter up to 10 microns, optionally together with a diluentor carrier, such as lactose, of the desired particle size distributionand a compound that helps to protect against product performancedeterioration due to moisture.

[0086] When the composition comprises a nebulised formulation, itpreferably contains, for example, a compound of formula I eitherdissolved, or suspended, in a vehicle containing water, a co-solventsuch as ethanol or propylene glycol and a stabiliser, which may be asurfactant.

[0087] The invention also includes (A) a compound of formula I ashereinbefore described in free form, or a pharmaceutically acceptablesalt or solvate thereof, in inhalable form; (B) an inhalable medicamentcomprising such a compound in inhalable form together with apharmaceutically acceptable carrier in inhalable form; (C) apharmaceutical product comprising such a compound in inhalable form inassociation with an inhalation device; and (D) an inhalation devicecontaining such a compound in inhalable form.

[0088] Dosages employed in practising the invention will of course varydepending, for example, on the particular condition to be treated, theeffect desired and the mode of administration. In general, suitabledaily dosages for oral administration are of the order of 0.5 to 200 mg,while suitable daily dosages for administration by inhalation are of theorder of from 0.1 to 10 mg.

[0089] The invention is illustrated by the following Examples.6-Amino-8-bromo-1,7-naphthyridine used in the Examples is prepared asdescribed in WO98/18796.

EXAMPLE 14[8-(3-Cyano-phenyl)-[1,7]naphthyridin-6-yl]-cyclohexanecarboxylic acidethyl ester

[0090] 6-amino-8-(3-cyanophenyl)-1,7-naphthyridine

[0091] To a mixture of tetrahydrofuran (THF) (80 ml) and 2 N sodiumcarbonate (34 ml, aqueous) is added 6-amino-8-bromo-1,7-naphthyridine(4.007 g), triphenylphosphine (0.37 g) and 3-cyanophenylboronic acid(323 g). The mixture is degassed under argon three times and thenbis(dibenzylideneacetone)palladium (0) (0.4 g) is added and the mixtureis degassed under argon three more times. The mixture is heated at 80°C. under argon for 16 hours then cooled and filtered. The mixture isdiluted with ethyl acetate and washed with 2 N sodium hydroxide thenbrine. After drying over sodium sulfate the organic layer is evaporatedand suspended in ether. The solid precipitate thus obtained is the titlecompound, which is filtered off. M.p. 182-184° C. HRMS [M+H]⁺found=247.1.

[0092] 6-Trifluromethanesulfonyl-8-(3cyanophenl)-1,7-naphthyridine—Compound A

[0093] To a solution of 6-amino-8-(3-cyanophenyl)-1,7-naphthyridine(4.058 g) in dimethylform-amide (DMF) (22 ml) under argon at 0° C. isadded trifluoromethanesulfonic acid (11 ml). The mixture is stirred at0° C. for 10 minutes and then sodium nitrite (2.26 g) is added slowly.The cooling bath is then removed and the mixture stirred at roomtemperature for 3 hours. The resulting mixture is diluted with ethylacetate and washed with water, 2 M NaOH and water again. The organiclayer is dried over sodium sulfate, then concentrated in vacuo andpurified by column chromatography, eluting with 10:0.5 toluene:acetoneto yield the title compound. M.p. 102-104° C. MS (m/e)=380.1

[0094] 4-Iodo-cyclohexanecarboxylic acid ethyl ester—Compound B

[0095] To a cold (0° C.) stirred solution of4-hydroxy-cyclohexanecarboxylic acid ethyl ester (1.0 g, 5.80 mmol) in1:2 CH₂Cl₂/CCl₄ (52 ml) is added triphenylphosphine (1.82 g, 6.96 mmol),imidazole (473 mg, 6.96 mmol), and iodine (1.79 g, 7.08 mmol). Thereaction is allowed to warm to room temperature and stirred overnight.The reaction is quenched by the addition of saturated sodiumthiosulphate (c.a. 50 ml) and stirred until the solution becomes clear.The layers are separated and the aqueous layer is extracted with CH₂Cl₂(3×30 ml). The combined organic phases are washed with sodiumthiosulphate (30 ml), brine (30 ml), dried with anhydrous MgSO₄,filtered and evaporated at reduced pressure to an oily solid.Purification by dry flash chromatography, Keiselgel 15-40 grade silica,eluting with 3% ethyl acetate/iso hexane yields the title compound as aclear colourless oil.

[0096]4-[8-(3-Cyano-phenyl)-[1,7]naphthyridin-6-yl]-cyclohexanecarboxylic acidethyl ester

[0097] A flask is charged with activated zinc dust (742 mg, 11.13 mmol),THF (1.80 ml) and 1,2-dibromoethane (25 μl 0.284 mmol). The suspensionis heated to reflux for 3 minutes and then allowed to cool beforetrimethylsilyl chloride (29 μl, 0.227 mmol) is added. The mixture isstirred for 15 minutes, then Compound B (1.60 g, 5.67 mmol) is added andthe mixture stirred at 35° C. for 1.5 hours. A second flask is chargedwith Pd (dibenzylideneacetone)₂ (101 mg, 0.176 mmol),1,1′-bis(diphenyl-phosphino)ferrocene (98 mg, 0.176 mmol),N-methylpyrrolidinone (NMP) (3 ml):THF (1 ml), tetrabutylammonium iodide(2.79 g, 7.56 mmol) and Compound A (956 mg, 2.52 mmol and the contentsare added to the first flask at 35° C. The reaction is stirred for 2hours, then quenched by the addition of water (15 ml) and stirred forten minutes. Ethyl acetate (40 ml) is then added and stirred for 5minutes. The layers are separated and the organic layer is washed with5% citric acid (25 ml), water (2×25 ml), and brine (40 ml), dried withanhydrous MgSO₄, filtered and evaporated to brown viscous oil.Purification is by dry flash chromatography using 15-40 grade Keiselgelsilica, eluting with 30% ethyl acetate/iso-hexane to yield the titlecompound as an orange gum. MH⁺ 386.0.

EXAMPLE 24-[8-(3-Cyano-phenyl)-[1,7]naphthyridin-6-yl]-cyclohexanecarboxylic acid

[0098] A solution of lithium hydroxide (6.5 mg, 0.155 mmol) in water(160 μl) is added to a solution of4-[8-(3-cyano-phenyl)-[1,7]naphthyridin-6-yl]-cyclohexane carboxylicacid ethyl ester (60 mg, 0.155 mmol) in NMP(0.16 ml). Upon completion,the reaction is diluted with water and washed with ethyl acetate (5 ml).The aqueous layer is acidified with 5% citric acid and the product isextracted into ethyl acetate. The organic layer is dried over brine (10ml) and anhydrous MgSO₄, filtered and evaporated. Purification by flashchromatography using Keiselgel 40-63 grade silica and eluting with 1.5%CH₃OH:0.5% CH₃COOH: dichloromethane affords the title compound. MH⁺357.0. mp 179.8-180.3° C.

EXAMPLE 34-[8-(3-Cyano-phenyl)-[1,7]naphthyridin-6-yl]-cyclohexanecarboxylic acid

[0099] Potassium Salt

[0100]4-[8-(3-Cyano-phenyl)-[1,7]naphthyridin-6-yl]-cyclohexanecarboxylic acid(24 mg, 0.067 m mol)) is dissolved in methanol (c.a. 2 ml) and anhydrousK₂CO₃ (4.6 mg, 0.035 mmol) is added. The suspension is ultra-sonicatedfor 15 minutes or until the K₂CO₃ is dissolved. Evaporation of themethanol and subsequent trituration of the resulting salt with bothethyl acetate and diethyl ether followed by drying gives the titlecompound. MH⁺ 357.0 (parent acid). Mp>250° C.

EXAMPLE 44-[8-(3-Carbamoyl-pheny4)-[1,7]naphthyridin-6-yl]-cyclohexanecarboxylicacid

[0101] Sodium hydroxide (4 M, 0.5 ml) is added to a solution of4-[8-(3-cyano-phenyl)-[1,7]naphthyridin 6-yl]-cyclohexanecarboxylic acidethyl ester (65 mg, 0.168 mmol) in NMP/CH₃OH/H₂O (0.50 ml, 8:1:1) andthe solution is left stirring overnight. The solution is acidified withaqueous 5% citric acid and extracted into ethyl acetate (3×10 ml). Theorganic layer is dried over brine, anhydrous MgSO₄, filtered andevaporated at reduced pressure to a yellow gum. Purification is by massspectrometry guided preparative HPLC (column: Xterra ms c8 5 μm 19×50mm) to give the title compound. MH⁺ APCI 376.0.

EXAMPLE 5 3-[6-(4-Carboxy-cyclohexyl)-[1,7]naphthyridin-8-yl]-benzoicacid

[0102] This is prepared analogously to Example 4, purification by massspectrometry guided preparative HPLC (column: Xterra c8 5 μm 19×50 mm)affording the title compound. MH⁺ APCI 377.1

EXAMPLE 64-[8-(5-Fluoro-2-methoxy-phenyl)-[1,7]naphthyridin-6-yl]-cyclohexane-carboxylicacid ethyl ester

[0103] This is prepared analogously to Example 1, fromtrifluoromethanesulfonic acid8-(5-fluoro-2-methoxy-phenyl)-[1,7]-naphthyridin-6-yl ester as thestarting material. MH+ APCI 409.0.

EXAMPLE 74-[8-(5-Fluoro-2-methoxy-phenyl)-[1,7]naphthyridin-6-yl]-cyclohexane-carboxylicacid

[0104] This is prepared, analogously to Example 2, from the product ofExample 6, the product being purified by mass spectrometry guided HPLC(column: Xterra ms c8 5 μm 19×50 mm) to give the title compound as ayellow gum. MH⁺ 381.1.

EXAMPLE 84-[8-(5-Fluoro-2-methoxy-phenyl)-[1,7]naphthyridin-6-yl]-cyclohexanecarboxylicacid sodium salt

[0105] This is prepared, analogously to Example 3, from the product ofExample 7, using anhydrous Na₂CO₃. MH⁺ 381.1 (parent acid seen).

EXAMPLES 9-19

[0106] By procedures analogous to the appropriate Examples above, andusing appropriate starting materials, compounds of formula I areobtained as identified in Table I together with mass spectrometrycharacterising data (MS:APCI MH⁺). The compounds are obtained in freeform, except for Example 11 that is isolated as the potassium salt.TABLE I Ex. No R¹ R² MS 9

368.6 10

362.9 11

388.184 12

350.6 13

367.0 14

417.65 15

379.05 16

395.87 17

347.06 18

386.8 19

407.16 20

377.12 21

381.16 22

333.71

EXAMPLE 104-[8-(3-Methoxy-phenyl)-[1,7]naphthyridin-6-yl]-cyclohexanecarboxylicacid

[0107] Potassium hydroxide (2 M, 0.9 ml) is added to a solution of4-[8-(3-Methoxy-phenyl)-[1,7]naphthyridin-6-yl]-cyclohexanecarboxylicacid ethyl ester (230 mg, 0.6 mmol) in THF/ethanol (6 ml:2 ml) andheated at 80° C. for 3 hours. The solution is then diluted with ethylacetate (120 ml) and extracted with water. The aqueous layer is taken topH 4 with 1M HCl to give a white precipitate, which is extracted intodichloromethane (DCM). The DCM layer is washed with water, then driedover magnesium sulfate, filtered and concentrated to yield the desiredproduct. M.p 209-212° C. MS (AP⁺) 362.9

[0108]4-[8-(3-Methoxy-phenyl)-[1,7]naphthyridin-6-yl]-cyclohexanecarboxylicacid ethyl ester

[0109] This compound is prepared in an analogous way to compound4-[8-(3-Cyano-phenyl)-[1,7]naphthyridin-6-yl]-cyclohexanecarboxylic acidethyl ester from trifluoromethanesulfonic acid8-(3-methoxy-phenyl)-[1,7]naphthyridin-6-yl ester. Purification is bychromatography followed by trituration with ether to yield a whitesolid. MS (AP⁺) 391.0

[0110] Trifluoromethanesulfonic acid8-(3-methoxy-phenyl)-[1.7]naphthyridin-6-yl ester

[0111] This compound is prepared in an analogous way to Compound A. MS(TOF ES+) 384.97

EXAMPLE 11 Potassium {4-[8-(3-cyano-phenyl)[1,7]naphthyridin-6-yl]-cyclohexyloxy}-acetate

[0112] Potassium carbonate (10.1 mg, 0.074 mmol) in water (1 ml) isadded to a solution of{4-[8-(3-cyano-phenyl)-[1,7]naphthyridin-6-yl]cyclohexyloxy}-acetic acid(59 mg, 0.15 mmol) in methanol (6 ml). The reaction mixture is stirredat room temperature for 30 minutes, filtered and concentrated. Theproduct is lyophilised from water (×3) then dried at 40° C. in vacuo for18 hours. Recrystallisation from CH₂Cl₂/ether gives the product. m.p148-150° C. (decomp.) MS (ES⁺) [M+H]⁺ 388.1635

[0113]{4-[8-(3-cyano-phenyl)-[1.7]naphthyridin-6-yl]-cyclohexyloxy}-aceticacid

[0114] Trifluoroacetic acid (TFA) (2 ml) is added to a solution of{4-[8-(3-cyano-phenyl)-[1,7]naphthyridin-6-yl]-cyclohexyloxy}-aceticacid tert-butyl ester (182 mg, 0.41 mmol) in CH₂Cl₂ (2 ml) at 0° C. Thesolution is stirred at room temperature for 1 hour, concentrated, andazeotroped with toluene (×3). Purification by chromatography on silicagel, eluting with 7% methanol in CH₂Cl₂ gives the product. MS (ES⁺)[M+H]⁺ 388.04

[0115]{4-[8-(3-cyano-phenyl)-[1.7]naphthyridin-6-yl]-cyclohexyloxy}-aceticacid tert-butyl ester

[0116] 1,2-Dibromoethane (12 μl) is added to a slurry of zinc dust (589mg, 9.0 mmol) in tetrahydrofuran (THF) (0.9 ml), The mixture is heatedat reflux for 3 minutes then allowed to cool to room temperature.trimethylsilylchloride (TMSCl) (15 μl) is added and the mixture isstirred at room temperature for 30 minutes.(4-iodo-cyclohexyloxy)-acetic acid tert-butyl ester (cis:trans=ca. 1:1)(680 mg, 2.0 mmol) in THE (1 ml) is added via syringe and the mixture isheated at 40° C. for 2 hours. A solution of Bu₄NI i.e.tetrabutylammonium iodide (1.1 g, 3.0 mmol), Pd(dba)₂ i.e. palladiumdibenzylideneacetone (40 mg, 0.07 mmol), dppf i.e.1,1′-bis(diphenylphosphino)ferrocene (39 mg, 0.07 mmol) and Compound A(372 mg, 1.0 mmol) in THF (2 ml)/NMP(2 ml) is added and the mixture isheated at 40° C. for 18 hours then allowed to cool to room temperature.The reaction mixture is diluted with ethyl acetate and filtered overCelite. The filtrate is washed with sat. aq. NH₄Cl (×1), 10% aq. citricacid (×1), water (×1) and brine (×1), dried (MgSO₄), filtered andconcentrated. Purification by chromatography on silica gel, eluting with30% ethyl acetate in isohexane gives the trans product. MS (ES⁺) [M+H]⁺444.10

[0117] (4-iodo-cyclohexyloxy)-acetic acid tert-butyl ester

[0118] Triphenylphosphine (1.18 g, 4.49 mmol), imidazole (0.31 g, 4.49mmol) and iodine (1.14 g, 4.49 mmol) are added to a solution of(4-hydroxy-cyclohexyloxy)-acetic acid tert-butyl ester (cis:trans=ca.1:1) (0.86 g, 3.74 mmol) in a mixture of CH₂Cl₂ (10 ml)/CCl₄ (20 ml) at0° C. The cooling bath is removed and the reaction mixture is stirred atroom temperature for 18 hours. Saturated aq. Na₂S₂O₃ (10 ml) is addedand the mixture is stirred for 15 minutes. The layers are separated andthe aqueous layer is re-extracted with CH₂Cl₂ (×3). The combined organicextracts are washed with brine (×1), dried (Na₂SO₄), filtered andconcentrated. Purification by chromatography on silica gel, eluting with5% ethyl acetate in isohexane, gives the product.

EXAMPLE 124-[8-(3-Fluorophenyl)-[1,7]naphthyridin-6-yl]-cyclohexanecarboxylic acid

[0119] Lithium hydroxide (1M (aq), 24.3 ml, 24.3 mmol) is added to asolution of4-[8-(3-fluorophenyl)-[1,7]naphthyridin-6-yl]-cyclohexanecarboxylic acidethyl ester (4.60 g, 12.14 mmol) in THF/methanol (40 ml:20 ml) andstirred at room temperature overnight. The organic solvents are removedby evaporation, then the aqueous residue diluted with water and basifiedto pH9 with 1M KOH. The aqueous layer is then washed with ethyl acetate(3×). The aqueous layer is acidified to pH 4 with 1M HCl to give a whiteprecipitate, which is extracted into ethyl acetate. The ethyl acetatelayer is then dried over sodium sulfate, filtered and concentrated toyield the desired product as a yellow foam. Further trituration with 1MHCl yields the product as a pale yellow powder (2.153 g). MS (AP⁺) 350.6

[0120]4-[8-(3-Fluorophenyl)-[1,7]naphthyridin-6-yl]-cyclohexanecarboxylic acidethyl ester

[0121] This compound is prepared in an analogous way to compound4-[8-(3-cyano-phenyl)-[1,7]naphthyridin-6-yl]-cyclohexanecarboxylic acidethyl ester from trifluoromethanesulfonic acid8-(3-flurophenyl)-[1,7]naphthyridin-6-yl ester. Purification is bychromatography followed by trituration with ether to yield a whitesolid. MS (AP⁺) 378.98

[0122] Trifluoromethanesulfonic acid8-(3-fluorophenyl)-[1,7]naphthyridin-6-yl ester

[0123] This compound is prepared in an analogous way to Compound A. MS(TOF ES+) 372.87

EXAMPLE 144-[8-(3-Trifluoromethoxyphenyl)-[1,7]naphthyridin-6-yl]-cyclohexane-carboxylicacid

[0124] Potassium hydroxide (2M (aq), 2.5 ml) is added to a solution of4-[8-(3-trifluoromethoxy-phenyl)-[1,7]naphthyridin-6-yl]-cyclohexanecarboxylicacid ethyl ester (250 mg, 0.56 mmol) in ethanol (10 ml) and stirred 45°C. for 1 h. The reaction mixture is diluted with water and acidifiedwith c.HCl to pH3. The mixture is stirred for 2 h. then filtered, andthe filter cake washed with water to yield the product as a white powder(218 mg). MS (AP⁺) 417.65

[0125]4-[8-(3-Trifluoromethoxyphenyl)-[1,7]naphthyridin-6-yl]-cyclohexanecarboxylicacid ethyl ester

[0126] This compound is prepared in an analogous way to compound4-[8-(3-cyano-phenyl)-[1,7]naphthyridin-6-yl]-cyclohexanecarboxylic acidethyl ester from trifluoromethanesulfonic acid8-(3-trifluromethoxyphenyl)-[1,7]naphthyridin-6-yl ester. Purificationis by chromatography followed by trituration with ether to yield a whitesolid. MS (AP⁺) 445

[0127] Trifluoromethanesulfonic acid8-(3-fluorophenyl)-[1,7]naphthyridin-6-yl ester

[0128] This compound is prepared in an analogous way to Compound A. MS(TOF ES+) 438.3

EXAMPLE 154-[8-(3-Methylsulfanyl-phenyl)-[1,7]naphthyridin-6-yl]-cyclohexanecarboxylicacid

[0129] Lithium hydroxide (168 mg, 1.76 mmol) in water (1.7 ml) is addedto a solution of4-[8-(3-methylsulfanyl-phenyl)-[1,7]naphthyridin-6-yl]-cyclohexanecarboxylicacid ethyl ester (650 mg, 1.6 mmol) in THF (3.2 ml) under argon.Methanol is added to maintain solution (4 ml) and the mixture is stirredat room temperature for 5 hours. The mixture is evaporated to drynessthen partitioned between ethyl acetate and water. The aqueous layer isacidified to pH 2 then extracted into ethylacetate and dried overmagnesium sulfate, Evaporation gives a green gum which is reevaporatedfrom methanol then DCM/diethylether to give a yellow/green foam. Thefoam is triturated with 3:1 hexane:diethyl ether, 2:1hexane:diethylether, ethylacetate/hexane/ether mixtures and finally 5:1diethylether:ethanol to yield an off-white solid. This is thenrecrystallised from ethanol to yield the title compound. M.p177.6-178.2° C., MS (AP⁺) 379.05

[0130]4-[8-(3-Methylsulfanyl-phenyl)-[1,7]-naphthyridin-6-yl]-cyclohexanecarboxylicacid ethyl ester

[0131] This compound is prepared in an analogous way to4-[8-(3-cyano-phenyl)-[1,7]naphthyridin-6-yl]-cyclohexanecarboxylic acidethyl ester from the analogous starting materials. MS (AP⁺) 407.2

EXAMPLE 164-[8-(3-Methanesulfinyl-phenyl)-[1,7]naphthyridin-6-yl]-cyclohexanecarboxylicacid

[0132] A solution of4-[8-(3-Methanesulfanyl-phenyl)-[1,7]naphthyridin-6-yl]-cyclohexane.carboxylic acid (30 mg, 0.079 mmol) in THF (1.4 ml) is cooled in asalt/ice bath and oxone (14.5 mg, 0.024 mmol) in water (0.5 ml) isadded. After 15 minutes the reaction mixture is allowed to warm to roomtemperature and after a further 30 minutes more oxone (14.5 mg isadded). The mixture is diluted with ethyl acetate/water and the aqueouslayer extracted with ethyl acetate. The combined organic layers arewashed with brine then dried over magnesium sulfate. Filtration followedby evaporation yields a foam consisting of title compound and4-[8-(3-Methanesulfonyl-phenyl)-[1,7]naphthyridin-6-yl]-cyclohexane-carboxylicacid. MS (AP⁺) 395.87

EXAMPLES 9, 13, 17, 18 and 22

[0133] Compounds of these Examples are made by an analogous procedure toExample 10 and may be isolated as either the free acid or as a salt, forexample the potassium salt.

EXAMPLES 19, 20 and 21

[0134] Compounds of these Examples are made by an analogous procedure toExample 11 and may be isolated as either the free acid or as a salt, forexample the potassium salt.

1. A compound of formula I

in free or salt form, where R¹ is a monovalent aromatic group having upto 10 carbon atoms, and R² is a cycloaliphatic group having up to 8 ringcarbon atoms.
 2. A compound according to claim 1, in which R¹ is phenylsubstituted by one or two substituents selected from cyano, halogen,carboxy or aminocarbonyl, and optionally by C₁-C₈-alkoxy, or R¹ isphenyl substituted by C₁-C₄-alkoxy, hydroxy or C₁-C₄-alkylthio, and R²is C₃-C₈-cycloalkyl optionally substituted by at least one substituentselected from C₁-C₄-alkyl, carboxy, C₁-C₈-alkoxycarbonyl oraminocarbonyl.
 3. A compound according to claim 1, in which R¹ is phenylsubstituted by one or two substituents selected from cyano, halogen,carboxy or aminocarbonyl meta to the indicated naphthyridine ring andoptionally by C₁-C₄-alkoxy ortho to the indicated naphthyridine ring, orR¹ is phenyl substituted by C₁-C₄-alkoxy meta to the indicatednaphthyridine ring, and R² is C₅-C₇-cycloalkyl optionally substituted byat least one substituent selected from carboxy and C₁-C₄-alkoxycarbonyl.4. A compound according to claim 1 in which R¹ is phenyl optionallysubstituted by one, two or three substituents selected from the groupconsisting of halo, cyano, C₁-C₈-alkyl, C₁-C₈-alkylthio,—SO—C₁-C₈-alkyl, C₁-C₈-alkoxy and C₁-C₈-haloalkoxy, or phenyl fused witha heterocyclic ring having 3 to 8 ring atoms of which up to 4 can becarbon atoms and up to 4 can be hetero atoms; and R² is C₃-C₈-cycloalkyloptionally substituted by at least one substituent selected from thegroup consisting of carboxy and carboxy-C₁-C₈-alkoxy.
 5. A compoundaccording to claim 1, in which R¹ is phenyl optionally substituted byone, two or three substituents selected from the group consisting ofhalo, cyano, C₁-C₄-alkyl, C₁-C₄-alkylthio, —SO—C₁-C₄-alkyl, C₁-C₄-alkoxyand C₁-C₄-haloalkoxy, or phenyl fused with a heterocyclic ring having 5or 6 ring atoms of which up to 4 can be carbon atoms and up to 2 can behetero atoms; and R² is C₅-C₇-cycloalkyl optionally substituted by atleast one substituent selected from the group consisting of carboxy andcarboxy-C₁-C₄-alkoxy.
 6. A compound according to claim 1, which is4-[8-(3-cyano-phenyl)-[1,7]naphthyridin-6-yl]-cyclohexanecarboxylic acidethyl ester,4-[8-(3-cyano-phenyl)-[1,7]naphthyridin-6-yl]-cyclohexanecarboxylicacid,4-[8-(3-cyano-phenyl)-[1,7]naphthyridin-6-yl]-cyclohexane-carboxylicacid potassium salt,4-[8-(3-carbamoyl-phenyl)-[1,7]naphthyridin-6-yl]-cyclo-hexanecarboxylicacid, 3-[6-(4-carboxy-cyclohexyl)-[1,7]naphthyridin-8-yl]-benzoic acid,4-[8-(5-fluoro-2-methoxy-phenyl)-[1,7]naphthyridin-6-yl]-cyclohexanecarboxylicacid ethyl ester,4-[8-(5-fluoro-2-methoxy-phenyl)-[1,7]naphthyridin-6-yl]-cyclohexanecarboxylicacid, or4-[8-(5-fluoro-2-methoxy-phenyl)-[1,7]naphthyridin-6-yl]-cyclohexanecarboxylicacid sodium salt.
 7. A compound according to claim 1, in which R¹ and R²are as listed in the following table: Ex. R¹ R² 9

10

11

12

13

14

15

16

17

18

19

20

21

22


8. (canceled)
 9. A pharmaceutical composition comprising a compoundaccording to claim 1, optionally together with a pharmaceuticallyacceptable diluent or carrier.
 10. (canceled)
 11. (canceled) 12.(canceled)
 13. (canceled)
 14. A process for the preparation of compoundsof formula I in free or salt form which comprises (i) (A) reacting acompound of formula II

optionally in protected form, where R¹ is as defined in claim 1 and L isa leaving atom or group, with a compound of formula III X—R²  IIIoptionally in protected form, where R² is as defined in claim 1 and X isa leaving atom or group which is reactive with L in formula II to form adirect bond between R² and the indicated naphthyridine ring, followed bydeprotection if required, or (B) reacting a compound of formula I, whereR² is cycloalkyl substituted by a C₁-C₈-alkoxycarbonyl group, to convertthe alkoxycarbonyl group into a carboxy group, and (ii) recovering theproduct in free or salt form.
 15. A compound according to claim 1 incombination with another drug substance which is an anti-inflammatory, abronchodilator, an antihistamine or an immunosuppressive drug substance,particularly a beta-2 adrenergic receptor agonist.
 16. A pharmaceuticalcomposition comprising a compound according to claim 6, optionallytogether with a pharmaceutically acceptable diluent or carrier.
 17. Apharmaceutical composition comprising a compound according to claim 7,optionally together with a pharmaceutically acceptable diluent orcarrier.
 18. A method of treating a condition mediated by PDE4 in asubject in need of such treatment, which comprises administering to saidsubject an effective amount of a compound of formula I as defined inclaim 1 in free form or in the form of a pharmaceutically acceptablesalt.
 19. A method of treating a condition mediated by PDE4 in a subjectin need of such treatment, which comprises administering to said subjectan effective amount of a compound of formula I as defined in claim 6 infree form or in the form of a pharmaceutically acceptable salt.
 20. Amethod of treating a condition mediated by PDE4 in a subject in need ofsuch treatment, which comprises administering to said subject aneffective amount of a compound of formula I as defined in claim 7 infree form or in the form of a pharmaceutically acceptable salt.
 21. Amethod of treating a condition mediated by down-regulation or inhibitionof TNF-α release in a subject in need of such treatment, which comprisesadministering to said subject an effective amount of a compound offormula I as defined in claim 1 in free form or in the form of apharmaceutically acceptable salt.
 22. A method of treating aninflammatory disease in a subject in need of such treatment, whichcomprises administering to said subject an effective amount of acompound of formula I as defined in claim 1 in free form or in the formof a pharmaceutically acceptable salt.
 23. A method of treating anobstructive or inflammatory airways disease in a subject in need of suchtreatment, which comprises administering to said subject an effectiveamount of a compound of formula I as defined in claim 1 in free form orin the form of a pharmaceutically acceptable salt.
 24. A method oftreating an obstructive or inflammatory airways disease in a subject inneed of such treatment, which comprises administering to said subject aneffective amount of a compound of formula I as defined in claim 6 infree form or in the form of a pharmaceutically acceptable salt.
 25. Amethod of treating an obstructive or inflammatory airways disease in asubject in need of such treatment, which comprises administering to saidsubject an effective amount of a compound of formula I as defined inclaim 7 in free form or in the form of a pharmaceutically acceptablesalt.